Summary of sql database statement optimization analysis and optimization techniques (sql optimization tool)-Mysql Tutorial-php.cn

Usually sql database needs to be optimized and analyzed, and there are certain skills. Several methods of sql optimization will not be introduced in detail here. This article will summarize the sql statement optimization, and the optimization tool SQL Tuning Expert is also attached. for Oracle and how to use it, first we must follow several principles of database optimization:

1. Try to avoid doing operations on columns, which will cause index failure;

2. Use join It is necessary to use a small result set to drive a large result set, and at the same time split the complex join query into multiple queries. Otherwise, the more tables you join, the more locks and congestion will occur.

3. Pay attention to the use of like fuzzy queries and avoid using %%, for example, select * from a where name like '�%';

Replace the statement: select * from a where name > = 'de' and name

4. Only list the fields that need to be queried, do not use select * from..., save memory;

5. Use batch Insert statements to save interaction;

insert into a (id ,name)
values(2,&#39;a&#39;),
(3,&#39;s&#39;);

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6. When the limit base is relatively large, use between ... and ...

7. Do not use the rand function to randomly obtain records;

8. Avoid using null, which requires setting it to not null as much as possible when creating a table to improve query performance;

9, do not use count(id), but count(*)

10. Don’t do unnecessary sorting, complete the sorting in the index as much as possible;

Let’s look at a sql first:

 select
                    ii.product_id, 
                    p.product_name, 
                    count(distinct pim.pallet_id) count_pallet_id, 
                    if(round(sum(itg.quantity),2) > -1 && round(sum(itg.quantity),2) < 0.005, 0, round(sum(itg.quantity),2)) quantity,
                    round(ifnull(sum(itag.locked_quantity), 0.00000),2) locked_quantity,
                    pc.container_unit_code_name,
                    if(round(sum(itg.qoh),2) > -1 && round(sum(itg.qoh),2) < 0.005, 0, round(sum(itg.qoh),2)) qoh,
                    round(ifnull(sum(itag.locked_qoh), 0.00000),2) locked_qoh,
                    p.unit_code,
                    p.unit_code_name
                from (select 
                        it.inventory_item_id item_id, 
                        sum(it.quantity) quantity, 
                        sum(it.real_quantity) qoh 
                    from 
                        ws_inventory_transaction it
                    where 
                        it.enabled = 1 
                    group by 
                        it.inventory_item_id  
                    ) itg 
                    left join (select 
                                    ita.inventory_item_id item_id, 
                                    sum(ita.quantity) locked_quantity, 
                                    sum(ita.real_quantity) locked_qoh 
                               from 
                                    ws_inventory_transaction_action ita
                               where 
                                    1=1 and ita.type in (&#39;locked&#39;, &#39;release&#39;) 
                               group by 
                                    ita.inventory_item_id 
                               )itag on itg.item_id = itag.item_id
                    inner join ws_inventory_item ii on itg.item_id = ii.inventory_item_id 
                    inner join ws_pallet_item_mapping pim on ii.inventory_item_id = pim.inventory_item_id  
                    inner join ws_product p on ii.product_id = p.product_id and p.status = &#39;OK&#39;
                    left join ws_product_container pc on ii.container_id = pc.container_id
//总起来说关联太多表，设计表时可以多一些冗余字段，减少表之间的关联查询；
                where 
                    ii.inventory_type = &#39;raw_material&#39; and 
                    ii.inventory_status = &#39;in_stock&#39; and 
                    ii.facility_id = &#39;25&#39; and 
                    datediff(now(),ii.last_updated_time) < 3  //违反了第一个原则
                     and p.product_type = &#39;goods&#39;
                     and p.product_name like &#39;%果%&#39;   // 违反原则3

                group by 
                    ii.product_id
                having 
                    qoh < 0.005
                order by 
                    qoh desc

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In the above sql, we used the subtitle in the from Query, this is very detrimental to the query;

A better approach is the following statement:

select  
                t.facility_id,
                f.facility_name,
                t.inventory_status,
                wis.inventory_status_name,
                t.inventory_type,
                t.product_type,
                t.product_id, 
                p.product_name,
                t.container_id, 
                t.unit_quantity, 
                p.unit_code,
                p.unit_code_name,
                pc.container_unit_code_name,
                t.secret_key,
                sum(t.quantity) quantity,
                sum(t.real_quantity) real_quantity,
                sum(t.locked_quantity) locked_quantity,
                sum(t.locked_real_quantity) locked_real_quantity
            from ( select 
                        ii.facility_id,
                        ii.inventory_status,
                        ii.inventory_type,
                        ii.product_type,
                        ii.product_id, 
                        ii.container_id, 
                        ii.unit_quantity, 
                        ita.secret_key,
                        ii.quantity quantity,
                        ii.real_quantity real_quantity,
                        sum(ita.quantity) locked_quantity,
                        sum(ita.real_quantity) locked_real_quantity
                    from 
                        ws_inventory_item ii 
                        inner join ws_inventory_transaction_action ita on ii.inventory_item_id = ita.inventory_item_id
                    where 
                        ii.facility_id = &#39;{$facility_id}&#39; and 
                        ii.inventory_status = &#39;{$inventory_status}&#39; and 
                        ii.product_type = &#39;{$product_type}&#39; and 
                        ii.inventory_type = &#39;{$inventory_type}&#39; and
                        ii.locked_real_quantity > 0 and 
                        ita.type in (&#39;locked&#39;, &#39;release&#39;) 
                    group by 
                        ii.product_id, ita.secret_key, ii.container_id, ita.inventory_item_id
                    having 
                        locked_real_quantity > 0 
            ) as t
                inner join ws_product p on t.product_id = p.product_id 
                left join ws_facility f on t.facility_id = f.facility_id
                left join ws_inventory_status wis on wis.inventory_status = t.inventory_status
                left join ws_product_container pc on pc.container_id = t.container_id            
            group by 
                t.product_id, t.secret_key, t.container_id

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Note:

1. Do not use subqueries in the from statement;

2. Use more where to limit and narrow the search scope;

3. Make reasonable use of indexes;

4. Check sql performance through explain;

Use the tool SQL Tuning Expert for Oracle optimizes SQL statements

For SQL developers and DBAs, it is easy to write a correct SQL based on business needs. But what about the execution performance of SQL? Can it be optimized to run faster? If you are not a senior
DBA, many people may not have confidence.

Fortunately, automated optimization tools can help us solve this problem. This is the Tosska SQL Tuning Expert for Oracle tool that I will introduce today.

Download https://tosska.com/tosska-sql-tuning-expert-tse-oracle-free-download/

The inventor of this tool, Richard To, Former chief engineer at Dell, with more than 20 years of experience in SQL optimization.